New York Jets quarterback Mark Sanchez (6) reacts on the field against the Jacksonville Jaguars during the first half at MetLife Stadium. / Debby Wong, USA TODAY Sports

by Alex Raskin, Special for USA TODAY Sports

by Alex Raskin, Special for USA TODAY Sports

EAST RUTHERFORD, N.J. - Mark Sanchez couldn't have asked for a better opportunity to secure the New York Jets' starting quarterback job Saturday night.

Not only was rookie Geno Smith sidelined with a sprained ankle, but Sanchez's prospects were buoyed by the visiting Jacksonville Jaguars, who committed five defensive penalties for 43 yards and muffed a punt in front of their own end zone during the first half of the 37-13 Jets' victory.

For Sanchez, who finished with 139 yards, a touchdown and an interception while completing 13 of 23 passes over three quarters, it was a chance to reclaim the job he seemingly lost when the Jets drafted Smith in the second round of April's NFL Draft. But instead of taking advantage of the situation, Sanchez left the door open for Smith prior to the third (and most important) game of the Jets' preseason - Saturday's matchup with the New York Giants.

"We're not willing to name a starting quarterback right now," Jets coach Rex Ryan said afterward. "Will we name one before the Giant game? I don't know. Right now, we're not comfortable making that decision."

Things started well enough for Sanchez, who has been the team's starter for the past four seasons.

He completed all three of his attempts on the first series, two of which went for first downs and a third, which was hauled in by tight end Jeff Cumberland for a 23-yard touchdown. Sanchez was a bit off on a sideline pass to running back Bilal Powell, but the Jaguars were whistled for a five-yard illegal contact penalty and the blemish was quickly erased.

Unfortunately for Sanchez, his opportunism began to fade on his first trip into the red zone. Following Powell's 28-yard run, Sanchez completed a three-yard screen to fullback Tommy Bohanon before throwing an incomplete pass behind the head of wide receiver Stephen Hill. The Jets settled for a field goal and a 10-3 lead.

"When the protection really held up well for us, Mark did a nice job throwing the football," Ryan said. "When we got in the red zone, it was tough sledding down there."

If Sanchez's first red-zone experience on Saturday was bad, his second and third were unmitigated disasters.

After intentionally throwing an incompletion at the feet of tight end Kellen Winslow, Sanchez was picked off by Marcus Trufant on a pass that should also have been thrown away (Trufant had Winslow blanketed).

"It was a tight lane," Sanchez said, adding, "I should have put it out in front of Kellen a little more and gave him a better chance to make a better play."

The Jets punted on their next possession but got another shot at the end zone before the half when the Jaguars muffed a punt on their own three-yard line to set the stage for Sanchez's biggest red-zone transgression.

He began the drive by ignoring a wide-open Clyde Gates in the end zone, instead opting to scramble for two yards and forcing the Jets to use their final timeout. And if that wasn't bad enough, Sanchez ended the half by wandering around-exhausting the clock-and tossing an incompletion. Had he delivered the ball before the game clock struck "0:00," the Jets would have had an opportunity for a field goal.

"That won't happen again," Sanchez said only a few minutes after Ryan had publicly accepted blame for the play. "That shouldn't happen. I got to get rid of that ball sooner and not scramble. I know better than that. It won't happen."

And in case Sanchez's red-zone issues weren't pronounced enough, the team scored touchdowns on its next two trips inside the 20 by exclusively running the ball.

Of course, Saturday's stinker wasn't an isolated incident and it didn't do anything to erase the images of Sanchez's last two games at MetLife Stadium-a three-interception performance that ended with backup Greg McElroy leading the Jets to a 7-6 win over the Arizona Cardinals and a 49-19 loss to the New England Patriots that featured the infamous "butt fumble."

Smith, meanwhile, hasn't seen any live action at MetLife Stadium but he did spend some time throwing passes to injured wide receiver Santonio Holmes prior to the game. As casual as it may have been, it was Smith's first performance in front of a New York audience since he and the West Virginia Mountaineers lost the 2012 Pinstripe Bowl to the Syracuse Orange.

"We'll play it day by day," Smith said. "Based on what I've been told, the competition is still open. We've got a long time to evaluate. We'll see. Any time I get a chance to compete, I'm going to take full advantage of it. I've got another week of practice coming up. I'm going to go out there with the right mentality and try to win the job."

Smith did play well in the Jets' first preseason game, completing six of seven passes for 47 yards before spraining his ankle in the loss to the Detroit Lions. Outside of an interception, Sanchez played well too, completing 10 of 13 passes for 125 yards and a touchdown.

In addition to Smith's ankle injury, McElroy also sat out of Saturday's game because of a sore ankle. Third-string quarterback Matt Simms finished the game for the Jets, completing all five of his passes for 73 yards.

Smith actually practiced on his sore ankle during the week (Ryan described his performance on Wednesday as "brutal"), but the Jets didn't see any point in risking his health for an exhibition.

"It's a lot different being in a red jersey than being in a green and white one," Ryan said when asked why Smith was allowed to practice but prevented from playing in Saturday's game. "And from that, the intensity that the opponent plays with, your escapability, obviously we did not feel it was prudent to play him in tonight's game."

The Jets have two more preseason games remaining, which means the quarterback competition could continue into the fourth and final exhibition when teams generally save their starters in favor of second and third stringers.